Antenna-based near-field optical microscopy and spectroscopy makes use of locally enhanced optical fields created near laser-irradiated metal nanostructures acting as local probes. Using threedimensional simulations based on the finite element method we study the electromagnetic fields near various optical antennas and we optimize their geometry in order to bring out a strong enhancement in a selected frequency range. Our results provide clear guidelines for the fabrication of efficient antenna structures and for improving the sensitivity of current near-field microscopy schemes.

The optimization of PhC waveguides is a key issue for successfully designing PhC devices. Since this design task is computationally expensive, efficient methods are demanded. The available codes for computing photonic bands are also applied to PhC waveguides. They are reliable but not very efficient, which is even more pronounced for dispersive material. We present a method based on higher order finite elements with curved cells, which allows to solve for the band structure taking directly into account the dispersiveness of the materials. This is accomplished by reformulating the wave equations as a linear eigenproblem in the complex wave-vectors k. For this method, we demonstrate the high efficiency for the computation of guided PhC waveguide modes by a convergence analysis.

Silica on Silicon (SoS) and Silicon on insulator (SOI) fabrication technologies are now yielding efficient photonic devices that have potential uses (e.g. routing and switching) in multigigabit optical backplane interconnect applications. The ever increasing demands for higher speed data handling and greater throughput on board both operational and experimental satellites necessitate an examination of these technologies for their robustness and performance in a space environment. One of the main environmental stressors on electronic and photonic components is the incident radiation flux. This paper reports results from the experimental testing of two classes of photonic devices; namely a SoS arrayed waveguide grating (AWG), and a SOI ring resonator. For a total ionizing dose of 300 kRad Co60 gamma irradiation, the SOI ring resonator showed induced spectral shifts as lower than 0.4 pm/kRad, and the SoS AWG showed a maximum shift of 0.03 pm/kRad in one channel. The relatively low AWG radiation sensitivity tempt us to say that these devices could be considered radiation hard for the telecom CL wavelength band (1550 nm) in which these measurements were made.

We present a measurement technique to quantify sidewall roughness inside planar photonic crystal (PhC) holes. Atomic force microscopy is used to scan hole cross-section profiles. By fitting a circle onto each scan line and subtracting this circle from the measurement data, a quantitative value for the deviation from the ideal cylindrical hole shape is extracted. We investigate the sidewall roughness of InP-based PhC holes depending on the nitrogen content of the semiconductor etching plasma. The existence of a trade-off between hole undercut and surface roughness by optimizing the flux of nitrogen during the plasma etching of the PhC holes is confirmed. We further quantify with this technique the influence of the direct-writing of octagons instead of circles by electron-beam lithography on the measured roughness.

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